Process for dewaxing oils



March 5, 1935. A. BERNE-ALLEN, JR

FROCESS FOR DEWAXINGOILSy Filed Oct. 19, 1932 wwwa@ Patented Mar. 5, 1935 PROCESS FOR DEWAXING OILS Allan Berne-Allen, Jr., Great Kills, N. Y., as-

signer to Standard Oil Development Company, a corporation of Delaware Application October 19, 1932, Serial No. 638,490

3 Claims.

'Ihis invention relates tothe production of low cold test hydrocarbon oils, especially those derived from petroleum.

yI have found that in certain types of oils, par- 5 ticularly those o-ils which have been subjected to treatment with hydrogen at high temperatures and pressures, the total wax content is frequently not distributed uniformly throughout the entire lubricating oil range, butthat the wax may be concentrated to a greater or less extent in certain'portions of the oil, particularly in the heavier portions. I have also found that it is possible to separate from these oils the particular fraction containing the major proportion of the wax, and that the removal of the wax from this fraction when isolated from the remainder ofthe oil is much less troublesome.

The present invention is particularly concerned with an improved method for producing low cold test oils from such stocks. The improvement comprises separating the lubricating oil stock from which the low cold test oil is to be produced into a lighter fraction and a heavier fraction and then subjecting only the heavier fraction, which will contain most of the wax, to dewaxing. The dewaxed heavier fraction may then be blended back with the undewaxed lighter fraction preliminarily removed. In this way I have found that the dewaxing of the heavier fraction of the oil may be effected more easily and completely so that even when blending this dewaxed portion with the undewaxed portion of the oil it is possible to obtain a final product which has a satisfactory pour point and cloud` point.

It should be understood that this method is dis,

tinguished from certain other methods of dewaxing in which the total wax contentA of the oil is concentrated more or less in one fraction before dewaxing, by the fact that in this method a deiinite portion of the wax-containing oil itself is iirst removed and only the remaining fractions are. dewaxed.

The method of carrying n out my improved method will be fully understood from'the following description read with reference tothe accompanying drawing which is a diagrammatic view in sectional elevation of a type of apparatus suitable for my purposes.

" Referring to the drawing, numeral 1 designates a supply tank for the oil to be dewaxed. The oil, especially if it is a hydrogenated distillate, should Abe topped first to the flash point desired in the iinished product. Pump 2 draws oil from tank 1 through line 3 and forces it through line 1 into Athe still through line 29 and collected in tank a still 5 wherein the oil may be subjected to distillation under vacuum. The lighter fractions of the oil pass out of still 5 through line 6 and cooler 7 and are collected in tank 8. It will be understood that other methods of separating the 5 oil into a lighter and heavier fractionmay be used with equally good results.

The heavier fractions ofthe oil are withdrawn from the still through line 9 and arepassed into a drum l0 which is iitted with a suitable agitating 10 means such as the stirrer 11. Drum 10 is disposed within a container 12 which is adapted to be iilled with a refrigerating mediumsuch as chilled brine or other cold liquid.

' A suitable diluent for ,use in dewaxing is stored 15 in tank 13. This diluent may comprisea naphtha, a liquefied normally gaseous ,hydrocarbon such as liquid ethane, propane Aor butane or anyy other suitable solvent that may be used in dewaxing. The diluentis introduced through line 20 14 into 'drum 10 wherein it is thoroughly mixed with the loil to be dewaxed. During the mixing of theoil and diluent the temperature of the brine bath surrounding drum 10 is maintained at a temperature well above the wax separation point of the oil, sayv for example -around 100 to F. -When the oil and diluent are thoroughly mixed the'temperature of the brine bath in container 12 is lowered to below the wax sepa-V ration point of the oil .whereupon wax: is caused to precipitate. The thoroughly chilled iiux is. withdrawn from drum 10V through line V15 and passed to a settlingdrum 16 which is disposed within acontainer 17 iilled with a refrigerating medium such as chilled brine or otherv cold medium. The precipitated wax is allowed to settle out in drum 16 and when completely settled the supernatant iiux maybe withdrawn therefrom through line 18 by pump 19 and passed through line 20 into tankr21. The dewaxed flux is withdrawn from tank 21 through line 22 by pump 23 and flows through line 24 Vinto a still 25 wherein the diluent is removed from4 the'oil by distillation. Vapors of the diluent. pass out of the still through line 26, are cooled in cooler 27 and the condensed diluent is then returned' to diluent supply tank 13 through line 28. The dewaxed oil, free from diluent, is withdrawn from 30. The wax sludge whichn Vsettles out in drum 16 mayf be removed therefrom through lines 31 and 32 or it may first be washed with diluent in order to extract as much of the oil contained therein as possible. Diluent for washing purposes is supplied from tank 13 through line 33 to auxiliary supply tank 34 from which the diluent may be introduced into drum 16 through lines 35, 36 and 3.1. 'I'he supernatant wash liquor may be withdrawn through line 18 and the oil may be recovered therefrom by distillation. This washing may be repeated one or more times. The nal washed wax sludge is then withdrawngfrom drum 16 through line 31 and passed through `lines 36 Aand 37 into a lter supply tank 38 from which it is withdrawn through line 39 and introduced into a lter press A4 0.. The settling, washing and filtering equipment may be disposed Within aninsu'lated cabinet 41 which is adapted to be maintained at a suitably low temperature.

Following the dewaxing of the heavy fraction of the oil, the dewaxed oil from tank 30 by means of line 30'v and the undewaxed oil from vtank .8 by means of line 8 may be conducted .to .a blending tank 42 and may be blended'to produce a nished oilof low .pour point and cloud point.

In -the 'operation of :my process it will be understood :that any method of dewaxing may `be employed, .and that although in the drawing -the cold settling Amethod has been illustrated, the process is not limited thereto. .Other lmethods such as centrifuging and ltering `may be used. Also, it should be .understood that the method of .dewaxing is not restricted v,to lany particular type of diluent. The essential yfeature `of the invention V.is the ypreliminary separation -from the oil of ,the lighter Wax-bearing fractions, the presence of which-during .the .dewaxing I `have found complicates the removal .of wax :from the heavier `portions of Ythe oil.

It will be understood (that lthe-0.5.1 `may be initially separated into Ytwo .fractions of .such .width that ythe yde waxed .heavyioil when .blended .back with the Vundewaxed 'light .oil will produce V.a blended oil -ofa y predetermir'ied pour point and cloud point. IngeneraLoils Aofsatisfactory pour point may be .obtained by removing .from `.50 to er 85% `of :the lighter portions ,of the oil .and

. then .dewaxing Yonly the remaining heavier ,fractions. It is not essential tofblend ,back t.the dewaxed heavy fractions -With the -lighter-frac tions igrst removed therefrom, Y for in some cases it may :be advantageous to fblend Ifback fthe adewaxed fractions with light fractions obtained.

from some other typeof oil. l

`The following example illustrates the .applicationof my improved method .of dewaxing2 A lubricating oil distillate obtained Vfrom -Colombian kcrude is vsubjected rto 'restricted K destructive 4hyd-rogenation and a hydrogenated lubricating distillate of improved Yquality is obtained from the product. This hydrogenated distillate is reduced to 50% 'bottoms and an oil corresponding .to a light -motor oil lis obtained. 'I'.his 50% bottoms loil has the following -characteristics:

Gravity, A.V'P."I c 26.7

Flash 420 F. Saybolt viscosity F 336 seconds Sayboltviscosity 210 F 551 seconds Pour point 20 F. Cloud point '36 F.

When this oil is dewaxed the pour point is reduced to 0 F. and the cloud point to below 0 F.

When however the lightest 70% of this oil is rst removed by vacuum distillation and only the remaining 30% residual is dewaxed, and the dewaxed 30% is blended back with the undewaxed '70%, the blend has a pour point of 0 F. and a cloud `point of 8 F. It will be observed that by dewaxing only the heaviest 30% `of the oil and then blending this back with the remaining undewaxed 70%, the nal oil has substantially the same pour point and cloud point as is obtained when the entire oil is dewaxed. TheV 30% residual may be dewaxed more easily than the entire lubricating `oil fraction, and the cost of processjing .is reduced in proportion to the percentage of the total lubricating stock dewaxed.

In asimilar experiment the heaviest 50% of the oil is dewaxed and then blended back with the remaining 50% of undewaxed oil and the blend is found to have a pour point of 0 F. -and a kcloud gpoint of below 0 F. Y

t is Vthus possible to dewax only a small proportion of a heavy oil and to blend Athis back with avery large proportion of undewaxed oil and-still obtain .an oil of suitably low cloud point and pour point. Such a method not only increases the :capacity of the dewaxing equipment but v.also facilitates the dewaxing of that .portion `of the yoil which is actually dewaxed.

This invention is not limited by any .theories of the mechanism yof dewaxing nor byanydetails or 4,data which have been .given merely for 4purposes .of illustration but is limited .only in and by the following claims in which I wish .to claim all novelty inherent in the process.

I claim:

l. An improved process for producing .oils -of low cold test from waxy hydrocarbon distillates of `the type in which the major proportion .of -the wax is found in the heavier fractions which comprises separating the distillate intoa lighter fraction of relatively low wax .content and a heavier fraction, removing .a substantial portion of the wax .from the heavier fraction, and then .blending the undewaxed'lighter fraction with .the .dewaxed `heavier fraction.V

2. An improvedprocess for producing lubrieating .oils of low cold test from waxy Adistillates derived from petroleum of the type in which the major proportion of the wax is found in the heavier fractionswhich comprises separatingthedistillate into tWo fractions, one containing a minor proportion of the wax content of the oil and the other containing a major proportion of the Wax content of the oil, removing .a substantial .proportion of the wax from the latter fraction, .and then blending the undewaxed fraction with the dewaxed fraction.

3. An' improved processior producing a low cold test lubricating oil from an oil prepared by the .destructive 'hydrogenation of a heavy petroleum fraction which comprises removing the nonviscous portions Vof the distillate, separatingthe topped 'hydrogenated oil into a lighter fraction and a 'heavier fraction, removing a substantial portion of the wax from the heavier fraction and then blending the undewaxed lighter fraction with the dewaxed heavier fraction.

SLLLAN BERNE-ALLEN, JR. 

